Various devices have been provided for preventing sticks, twigs and leaves from collecting in and blocking the flow of rainwater through eaves troughs. Wire screening commonly serves as a protective cover for upwardly open eaves troughs. The screening must be periodically cleaned to prevent the accumulation of leaves and sticks thereon. Such accumulation not only is unsightly, but also can form a largely impervious cover over the upwardly open troughs, preventing rain water from entering the troughs. Further, the accumulation of leaves and other debris can hinder the free run-off of snow from roofs, ultimately leading to damage from ice formation under the roof shingles.
U.S. Pat. No. 603,611 (Nye) describes a gutter having a reversely curved strip of metal providing a smooth surface over which water from the roof would flow outwardly, downwardly and then back inwardly to be captured in a trough. This patent suggested that debris entrained in the water would fall from the generally vertical section of the smooth surface. In commenting upon the Nye invention, Bartholomew, U.S. Pat. No. 669,950, states that wet leaves, pieces of paper and other flexible objects that have great surface area would not fall from the smoothly curved surface of the Nye device, but rather would remain entrained in the water film and would be deposited in the trough portion of the device. To solve this problem, Bartholomew provided the curved surface with small, outwardly and downwardly oriented projections, Bartholomew's concept being that such projections would raise leaves, pieces of paper and the like from the flowing water film, permitting them to drop to the ground. A somewhat different design is shown in Cassens U.S. Pat. No. 891,405. The eaves trough described in this patent includes a generally flat, inclined upper wall, a trough beneath the upper wall, and a tight, generally S-shaped connection between the upper wall and the trough providing a curved surface over which rain water passes. The S-shaped portion includes uowardly open slots or orifices for straining debris from the rain water. A somewhat similar device is shown in Foster, U.S. Pat. No. 3,388,555, the latter patent showing an eaves trough having upwardly open, staggered slots for straining debris from the rain water.
In general, an upwardly open screen or other straining device carried by an eaves trough provides a place where leaves, sticks and other debris may collect to plug the straining device. Yet, with an eaves trough structure having a smooth, outer surface over which water is to run outwardly, downwardly and then inwardly toward a gutter, it is difficult to provide a straining device that on the one hand is not susceptible to becoming plugged with debris but on the other hand does not itself interrupt or divert the free flow of water along the smoothed, curved surface into the trough portion of the structure.